The known electronic components often have a hermetically sealed housing to ensure reliable functioning of the MEMS placed therein. The housing is usually made of two parts which consist of or were cut out of semiconductor wafers. At the locations where a cavity for placement of the MEMS is required, a recess is created in one or both parts of the housing by means of known etching methods, for example. The two housing parts can then be joined together permanently by known methods. Min and Rebeiz discuss such joining methods (Byung-Wook Min and Gabriel M. Rebeiz in IEEE Transactions on Microwave Theory and Technique, Vol. 54, No. 2, February 2006, pages 710ff.: “A Low-Loss Silicon-on-Silicon DC110 GHz Resonance-Free Package”).
One possibility for joining the parts consists of using so-called “glass frit” bonding methods, but these methods must be carried out at high temperatures that can lead to thermally induced stresses and the like in the component. Therefore, metallic bond frames are often used. These are arranged peripherally around the desired cavity, for example, and are then “welded” together by means of a bonding technique. This does not require the use of very high temperatures such as those required in glass frit bonding. The metallic bond frames may also be designed to be narrower.
Furthermore, there is a technical requirement that electrical high-frequency signals be introduced into the interior of the housing, so that signal feedthroughs are required. In the case of high-frequency signals, the technical problem is that cross-talk with the signal can occur on the metallic bond frames and therefore the signal feedthrough deteriorates at certain frequencies, i.e., losses occur. This is true in particular when the signal line in the interior of the housing is implemented as a micro-strip line (MSL).
Known components have configurations and/or concepts with which the signal deteriorations due to parasitic couplings between the metallic bond frames and the feedthroughs and/or the lines running through the feedthrough are to be reduced. Thus, for example, Margomenos and Katehi as well as Yu and Liao describe concepts, in which the signal line runs inside and outside of the housing as a coplanar line and the lines are connected via a vertical feedthrough through three parallel vias (though-silicon vias, abbreviated: “TSVs”) (Margomenos, A. and Katehi, L. P. B. at the 34th European Microwave Conference, Amsterdam, 2004, pages 645 ff.: “Ultra-wideband three-dimensional transitions for on-wafer packages” as well as Yu, W. and Liao, X. at the International Conference on Electronic Packaging Technology and High Density Packaging, IEEE, 2009, pages 201 ff.: “Design and simulation of a package solution for millimeter wave MEMS switch”).
These configurations create less coupling with the bond frame, but an even greater need for reduction has already been described by Lim et al. (Lim, Y. Y. et al. at Transducers 2011, Beijing, June 2011, pages 406 ff.: “A broadband 3D package for RF MEMS devices utilizing through-silicon vias TSV”). Further reduction in unwanted signal deterioration should be achieved according to Lim et al. through additional free-standing TSVs in the cavity.
However, there is still parasitic coupling with this configuration, so there is still a demand for optimization of the signal deterioration.
Furthermore, the researchers Min and Rebeiz mentioned above have pursued another configuration, in which a lateral feedthrough is provided with a thin insulation layer from the bond frame. The negative effects of the relatively strong coupling thereby induced are suppressed by removing the thin insulation layer beyond the signal line and connecting the bond frame and ground of the coplanar line. However, this configuration is relatively complex from the standpoint of production of the component. In addition, a component having a lateral feedthrough can be integrated into a circuit board only with great effort. For good signal transmission from the circuit board to the component, it is necessary to create packets in the circuit board to hold the component and to bring the terminal contacts to the same level as the terminal contacts on the circuit board. The electrical connection is usually supplied by bond wires. However, creating the pockets in the circuit board and the electrical connection with the bond wires are relative complex and therefore also expensive procedures.
There is a demand for an electronic component for integration of micro-devices in a cavity in the component, wherein high-frequency signals can be introduced into the interior of the component and output out of the interior of the component by means of high-frequency signal lines without any deterioration of the signals due to parasitic coupling to the component or parts thereof. Furthermore, there is a demand for a component that can be manufactured less expensively.
According to one aspect of the disclosure, an electronic high-frequency component is described for accommodating micro-devices, comprising at least two housing components which may be connected to one another by means of a metal frame and may include a cavity as described here. The cavity may preferably be arranged inside the metal frame.
The high-frequency component (“component” in short) may thus have at least one input signal line and optionally also at least one output signal line. The input and output signal lines (if the latter is present) may each be connected to a signal line via. In the optional case when at least one input signal line and at least one output signal line are to provided, the respective signal line via (inside the cavity or inside the bond frame) may be arranged at a distance from one another and connected to one another at least by means of an internal signal line. The aforementioned connection of the two signal line vias does not rule out the possibility that for the case when the internal signal line is to be connected to a MEMS switch or the like, the internal line is interrupted electrically in certain switch states of the switch.
Furthermore, the component described here may have at least one short-circuit via, which can electrically connect the metal frame to one of the housing components (preferably to a metallic ground surface on the housing component) of the component.
The short-circuit via may preferably be arranged inside the metal frame and/or the cavity. Alternatively or additionally, the short-circuit via may also be arranged outside of the cavity and therefore not inside the metal frame. It is thus optionally also possible to arrange a short-circuit via outside of the metal frame. Furthermore, an electrical connection in the form of a line, which runs along the outside of the chip and thus connects the metal frame to a (large) ground (surface) on the outside, may optionally also be established. This electrical line can be manufactured by metallization of a side wall of a housing part, for example.
The metal frame may preferably be a metallic bond frame, which preferably has a rectangular, square or round cross section. The advantage of the metal frame was already explained above. Among other things it does not require high temperatures for joining the housing parts, as is the case with glass frit bonding methods, for example. The metal frame may preferably be provided between the preferably two housing parts (more than two housing parts are also possible). The cavity may be created, for example, by means of known etching methods in at least one of the housing parts. The housing parts may preferably be semiconductor wafers or parts thereof. Silicon wafers in particular wafers made of highly resistive silicon are especially preferred. Alternatively the housing parts may also be made of glass, quartz or a ceramic.
The via(s) is/are preferably electrically conductive and in particular are preferably made of metal.
The at least one micro-device may be a microelectromechanical or micro-optoelectro-mechanical system (MEMS/MOEMS) or a corresponding nano system. One example of a MEMS system would be a switch in a high-frequency signal line. It should be pointed out that the cavity according to a particularly preferred alternative may be provided only for the accommodation of the MEMS and in particular may then be designed to be much smaller than the bond frame.
The component described here thus has the technical advantage that production is relatively uncomplicated because among other things it is not necessary to produce signal feedthrough insulation, which would then have to be removed again from predetermined locations in another complicated procedure. Furthermore, the component can be integrated into a circuit board inexpensively. In addition, this yields the technical advantage that the cavity is shielded from the penetration of dirt, moisture and the like because of the permanent bonding of the housing parts and the metal frame, and at the same time a high-frequency signal can be introduced into the housing which is hermetically sealed by means of the metallic bond frame without any deterioration of the signal due to parasitic coupling of signal line and bond frame.
The technically advantageous suppression/minimization of signal deterioration in input and/or output of the signal is preferably achieved here as follows: an electromagnetic wave or a portion thereof transmitting the signal can couple into the metal frame in passing through the input line and/or output line. In other words, a portion of the electric power and/or the signal can jump into the metal frame and propagate there. The resulting signal loss is suppressed and/or reduced here by the fact that the electrical short circuit, created by the short-circuit via, between the housing part and/or ground and/or a metal surface arranged on the housing part on which the input and/or output lines are arranged, and the metal frame leads to reflection of the electromagnetic wave that is input. The reflection then leads to a mutual elimination with the input electromagnetic wave. The technical effect described here can also be described differently, so that the length of the resonator or the metal frame here is reduced by one-half or is at least shortened (depending on the placement of short-circuit via), so that the resonant frequency is doubled and/or increased accordingly and therefore is no longer in the signal spectrum.
Furthermore, according to additional preferred aspects, at least one short-circuit via may also be arranged at the side of the input and output signal lines (if the latter is present). The short-circuit via(s) may in particular be placed as close as possible to one side of the input and/or output signal lines. Preferably, a short-circuit via may be arranged on each side of the input and output signal lines (if the latter is present). This side-by-side arrangement has shown that destructive reflection can be created in the metal frame especially effectively, so that minimization of signal interference is particularly effective.
Preferably, for example, with one input signal line and one output signal line as well as two short-circuit vias arranged side by side (i.e., four), these four short-circuit vias may be placed inside the metal frame in order to achieve a particularly effective reduction of signal interference.
Preferred positions for the arrangement of a short-circuit via can be found at the middle of a side edge and/or the corner of a side edge of the component and/or of the metal frame, in particular when fundamental oscillations of the resonator are to be influenced.
According to an alternative or additional aspect, one (or more) short-circuit via(s) may be embodied by means of a metallized side wall of at least one of the two housing parts. This means in particular that a via can be established by metallization of one part or an entire side wall, wherein the metallized side wall and/or its metal layer then establishes the electrical short circuit between the frame and ground. The side wall may preferably be an exterior wall of the housing part and need not be completely metallized. As in the case of the short-circuit vias described above, an electrical short circuit between the metal frame and ground of the input and/or output signal lines is established by means of metallization and can thus greatly reduce or even prevent the signal interference described above. This embodiment has the technical advantage that it permits a design of the component that is optimized with regard to installation space.
According to other aspects, the internal signal line may be a coplanar line or preferably a micro-strip line which can connect a micro-device electrically to the input and output signal lines. The input and output lines may preferably be coplanar lines. These short-circuit via(s) may preferably connect an electrical ground of the input and output lines electrically to the metal frame. The electrical ground may be part of one of the housing parts or may be arranged thereon. Use of micro-strip lines (in comparison with coplanar lines) in combination with silicon housing parts has the advantage that there are little or no losses due to conductive boundary layers between the silicon and silicon oxide.
According to another aspect, the vias may be arranged vertically to the cavity, i.e., vertically to the housing parts arranged in parallel to one another. Thus a vertical feedthrough of a high-frequency signal into a hermetic housing by means of a metal bond frame is possible without any signal deterioration due to the coupling of the signal line and the bond frame. This permits a broadband signal feedthrough. Vertical feedthrough also has the technical advantage that no other insulation of the signal lines need be applied, such as that which would be necessary with a lateral feedthrough, for example, and would make production more complex. Integration of the component on a circuit board is also facilitated by the vertical arrangement. Thus, for example, the component can be integrated inexpensively onto the circuit board and with relatively little effort by using a soldering method, with the terminal contacts on one of the two large exterior surfaces like a regular SMD component (surface mount device component).
According to another aspect, one or more feedthroughs, in which the signal line via can be arranged, may be arranged inside the metal frame. Preferably, the feedthrough and/or signal line via may be arranged in a position in which there is a large difference (or preferably the maximum difference) between the surge impedance of the input or output signal line and that of the metal frame. This positioning of the feedthrough(s) permits a further substantial reduction in the signal interference because coupling of the signal wave into the metal frame is initially hindered and, additionally, the elimination of a wave, which can nevertheless be input, can be extinguished by means of the short-circuit vias.
According to another aspect, the component and/or the housing parts may have a rectangular, round or square shape to achieve the handiest possible shape. The metal frame may preferably be arranged on an outer edge of the component and/or the two housing parts, especially preferably being flush with same. Furthermore, the metal frame may have a width of a few micrometers up to several tens of micrometers to achieve the most secure possible seal, i.e., encapsulation of the cavity. Values between 50 μm and 300 μm are preferred, for example.
Furthermore, the signal line vias of electrically interconnected signal input lines and output lines may be arranged so that they are opposite one another (as seen across the cavity), so that the line(s) between the signal line vias may be designed to be as linear/straight as possible.
According to another aspect, the input and output signal lines may each be arranged on the same housing part as the internal signal line. Alternatively, the input and output signal lines may also be arranged on a first housing part, and the internal signal line may be arranged on the second housing part. Preferably, the signal line vias may connect the internal signal line electrically (vertically) to the input and output signal lines so that a vertical feedthrough of the high-frequency signal through the signal line vias is made possible.
In summary, an electronic component is presented here for handling of high-frequency signals, requiring less manufacturing effort and reducing signal deterioration on input and output of high-frequency signals into and out of the cavity of the component in the best possible way. Furthermore, the component can be integrated more easily into a circuit board in particular due to the arrangement of the signal line vias.
The electronic component presented here is described in detail below as an example with reference to the accompanying schematic drawings, in which: